MMBe HEX & frequency questions.
acliffhay
Posts: 5
Good afternoon. I haven't been here in a long while...it's good to have a project to bring me back!
I'm using a BS2P40 with MMbe to control a Pittman 12VDC gear motor with encoder, and I need to be able to adjust the frequency(Speed) on the fly.
If 100Hz is the absolute slowest speed my motor can handle before it stalls or the MMBe H Bridge just won't activate, how can I calculate the approximate HEX values for a given duty cycle? (ie. 15%, 25%, 33%, 50%, 66%, 75%, 100% ) By using the SetDc command, I can set duty cycle just fine, however, the motor eventually stalls at the slowest setting. If I use the SpdCon command, the MMbe sends more power to the motor to maintain frequency of the tach giving me the extremely slow speeds I am looking for (Total drive ratio = 928.2:1) without stalling. I just can't seem to grasp the best way to find the frequencies I'm looking for and converting them to HEX variables to adjust frequency up or down during runtime. I'm sure you're wondering why I need to go soooo slow...I'm building a rotary welding/soldering/brazing fixture. I don't expect anyone to solve this for me, but some advice pointing me in the right direction would be fantastic! Thanks,
Al
I'm using a BS2P40 with MMbe to control a Pittman 12VDC gear motor with encoder, and I need to be able to adjust the frequency(Speed) on the fly.
START_UP:
'Send TACH command and read back/display tachometer frequency
'
SEROUT FM,1021,[noparse][[/noparse]$55,$82]
SERIN TM,1021,500,NO_CONFIRM4,[noparse][[/noparse]B7,B8, B9]
IF B7 = $AA THEN CONFIRM4
CONFIRM4:
DEBUG HOME
DEBUG "TACH VALUE = "
DEBUG ISHEX2 B8
DEBUG ISHEX2 B9,CR
NO_CONFIRM4:
'
'Send SPDCON command, freq. set to 100Hz('0064'h)
'
SpdCon:
SEROUT FM,1021,[noparse][[/noparse]$55,$84,$00,$64]
SERIN TM,1021,100,NO_CONFIRM5,[noparse][[/noparse]B7]
IF B7 = $AA THEN CONFIRM5
CONFIRM5:
DEBUG "SPDCON MODE",CR
NO_CONFIRM5:
PAUSE 250
GOTO Start_up
If 100Hz is the absolute slowest speed my motor can handle before it stalls or the MMBe H Bridge just won't activate, how can I calculate the approximate HEX values for a given duty cycle? (ie. 15%, 25%, 33%, 50%, 66%, 75%, 100% ) By using the SetDc command, I can set duty cycle just fine, however, the motor eventually stalls at the slowest setting. If I use the SpdCon command, the MMbe sends more power to the motor to maintain frequency of the tach giving me the extremely slow speeds I am looking for (Total drive ratio = 928.2:1) without stalling. I just can't seem to grasp the best way to find the frequencies I'm looking for and converting them to HEX variables to adjust frequency up or down during runtime. I'm sure you're wondering why I need to go soooo slow...I'm building a rotary welding/soldering/brazing fixture. I don't expect anyone to solve this for me, but some advice pointing me in the right direction would be fantastic! Thanks,
Al
Comments
If I need 350Hz (15E), do I code that as
If I'm correct, then can I create variables, say SPD1 = $01 and SPD2 = $5E and code them like this?
Al
Freq_Cmd VAR Word
Freq_Cmd=Input a value here
SEROUT FM,1021,[noparse][[/noparse]$55,$84,Freq_Cmd.HIGHBYTE,Freq_Cmd.LOWBYTE]
Jeff T.
Al H.